Many systems with multiple processors operate those processors with independent clocks. Since real-time processor trace outputs are synchronous with the processor clocks, a debug instrument capable of receiving and correlating multiple trace streams must account for the multiple clock domains.
One approach to addressing this problem is to record each processor's trace using an independent instrument, each of which uses the clock source associated with a given processor. This technique facilitates the reliable recording of trace information. However, it is difficult to correlate the independently timed trace information. To address this problem, some systems record a trigger into all buffers at a synchronization point and then present activity from the trace point forward in time order knowing the rate at which the trace clock for each buffer operates. The problem with this approach is that a typical clock source has limited accuracy. Due to clock uncertainty and drift, time alignment is lost after a few thousand cycles from the synchronization point.
In view of the foregoing, it would be desirable to provide an improved technique for tracing information from multiple clock domains.